[unreadable] [unreadable] This proposal is to request support for a Keystone Symposia meeting entitled "Stem Cell Interactions with their Microenvironmental Niche", which will be held in Keystone, Colorado from March 2-7, 2007. Stem cells are defined by their function in complex microenvironments that are just beginning to be defined. The architecture of these anatomic sites in molecular, cellular and developmental terms has provided insight into how tissues are formed and maintained throughout life. They now provide an opportunity for examining settings of disease and offering a distinct group of possible therapeutic interventions. This meeting will examine select stem cell niches to explore unifying principles and identify opportunities for application in tissue regeneration and cancer therapy. [unreadable] [unreadable] [unreadable]